Dipoles with 15-20 T operating field are required for some designs of future hadron colliders. Such dipoles require the use of high-field superconductors Nb3Sn, Bi-2212, and REBCO. Designs are presented for block-coil dipoles using superconducting cable-in-conduit. This approach conveys several benefits that are important for high-field operation: cable-level stress management; compact, robust flared ends; and in-cable cryogen flow. It naturally accommodates a hybrid coil configuration in which sub-windings of Bi-2212, Nb3Sn, and NbTi can be separately heat-treated, assembled, and preloaded in a compact assembly.